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Other Hybridisation Forms
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<H2 CLASS="section"><A NAME="htoc254">17.6</A>&nbsp;&nbsp;Other Hybridisation Forms</H2>
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This module has covered a few forms of hybridisation between <TT>ic</TT>
and <TT>eplex</TT>.
There are a variety of problem decomposition techniques that support
other forms of hybridisation. Three forms which employ linear duality
are <EM>Column Generation</EM>, <EM>Benders Decomposition</EM> and <EM>Lagrangian Relaxation</EM>. 
All three forms have been implemented in ECL<SUP><I>i</I></SUP>PS<SUP><I>e</I></SUP> and used to solve
large problems, and the ECL<SUP><I>i</I></SUP>PS<SUP><I>e</I></SUP> library <TT>colgen</TT>, described in
the next chapter, supports Column Generation.<BR>
<BR>
Often it is useful to extract several linear subproblems and apply a
separate linear solver to each one. The <TT>eplex</TT> library offers
facilities to support multiple linear solvers. Space does not permit
further discussion of this feature.<BR>
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Cooperating solvers have been used to implement some global
constraints, such as piecewise linear constraints [<A HREF="tutorial133.html#Refalo99"><CITE>21</CITE></A>].
Linearisation of <TT>ic</TT> global constraints
is another method of achieving tight cooperation.<BR>
<BR>
Finally many forms of hybridisation involve different search
techniques, as well as different solvers. For example stochastic
search can be used for probing instead of a linear solver, as described
in [<A HREF="tutorial133.html#cp99wkshoptalk"><CITE>28</CITE></A>].<BR>
<BR>
In conclusion, ECL<SUP><I>i</I></SUP>PS<SUP><I>e</I></SUP> provides a wonderful environment for exploring
different 
forms of hybridisation.<BR>
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